Crystallization and X-ray diffraction of a halogenating enzyme, tryptophan 7-halogenase, from Pseudomonas fluorescens

Abstract

Chlorination of natural products is often required for their biological activity; notable examples include vancomycin, the last-ditch antibiotic. It is now known that many chlorinated natural products are made not by haloperoxidases, but by FADH2-dependent halogenases. The mechanism of the flavin-containing enzymes is obscure and there are no structural data. Here, crystals of PrnA (tryptophan 7-halogenase), an enzyme that regioselectively chlorinates tryptophan, cocrystallized with tryptophan and FAD are reported. The crystals belong to the tetragonal space group P4 3212 or P41212, with unit-cell parameters a = b = 67.8, c = 276.9 Å. A data set to 1.8 Å with 93% completeness and an Rmerge of 7.1% has been collected from a single flash-cooled crystal. A method for incorporating selenomethionine in a Pseudomonas fluorescens expression system also is reported. © 2004 International Union of Crystallography.